Steel-making vessels

ABSTRACT

An insert 6 is pushed into an eroded tap hole 5 of a steel-making vessel. This insert has outer and inner plates 7 and 8 formed from relatively thin steel sheet or cardboard which will flex so as to adapt itself to the internal dimensions of the tap hole 5 as shown. Between the two plates 7 and 8 there is a tubular support member 9 defining a central passage-way 10 which has holes 11 formed on its side walls which communicate with the open volume 12 between the end plates 7 and 8. A supply hose 13 is connected to the tubular member 10, through which a settable material comprising a clay and binder in wet form is injected so that the whole volume between the end plates 7 and 8 is filled. At the temperatures experienced the clay material will set rapidly so as to block off the tap hole 5. When the steel has been formed and the steel-making vessel is tipped to enable the molten steel to be poured off through the tap hole, the hot molten material will rapidly melt the steel insert 6 and the set clay material, thus re-opening the tap hole 5.

When steel is being formed, the raw materials are fed into a heatedvessel and the formed molten steel is ultimately poured out through atap hole in a side wall as the vessel is tipped. It is highly desirablethat the tap hole should be blocked off during the steel-making processfor two main reasons. Firstly, this prevents the passage of air throughthe tap hole into the interior of the vessel during the forming of thesteel, which helps to control the nature of the gas within the vesselduring the forming process. Secondly, when the vessel is tipped to pourout the molten steel it is important to avoid the possibility that theslag floating on top of the steel should pass through the tap hole asthe edge of the liquid first arrives at the tap hole.

Because of the conditions, particularly extremely high temperatures,existing in the area of the steel-making vessel, and the fact that thetap hole attains a very irregular shape with use, it is difficult toachieve blocking of the tap hole and it is an object of this inventionto alleviate this particular problem.

Accordingly, the invention provides a tap hole blocking insert for asteel-making vessel comprising a former constructed from a materialwhich is stable at low refractory temperatures, but which will melt athigh refractory temperatures, and which is sufficiently flexible to bendwhen inserted into the tap hole, the former defining a centre cavity,open at the sides, between two end plates shaped to grip the sides ofthe interior of the tap hole, and an inlet passageway leading to thecavity for the injection of a settable material.

The low refractory temperatures referred to above are those which arelikely to be experienced in the region of the tap hole during thesteel-forming process and these typically might be within the region of600° to 700° C.

The invention also extends to a method of blocking a tap hole, using aninsert of this invention as hereinbefore defined, which comprisesintroducing the insert into the tap hole whilst the steel-making vesselis in the upright condition, and pressing the insert home as a tight fitwithin the tap hole, followed by injection of a material in wet formwhich will set at the low refractory temperatures to fill the spacebetween the plates of the insert so as to block the tap hole, the setmaterial being such that it will melt when subjected to the highrefractory temperatures experienced during pouring of the molten steel.

In one embodiment the insert may have an axial support member connectedbetween the plates but having holes in its side walls through which thesettable material can pass. Alternatively the end plates may be heldapart by spacer rods so as to define the centre cavity. These rods areideally threaded so that the distance between the end plates may bevaried as required and fixed by means of nuts.

In the preferred arrangement the edges of the plates of the insert aredesigned to flex as the insert is pressed into the tap hole so that theinsert will adapt itself to the irregular shape of the tap hole. Aparticular preferred material for forming the end plates of the formeris cardboard which has been found to have the necessary stability toremain in place at the high temperatures experienced for long enough toenable the settable material to be injected and set. For this purpose,therefore, cardboard is regarded as a material which is stable at lowrefractory temperatures. If desired, the cardboard sheets could becoated or impregnated with a flame-retardant solution. The use ofcardboard is particularly suitable since it is flexible and thus willadapt to the irregular shape of the hole being blocked. Advantageouslyradially extending cuts will be formed in the outer edges of the endplates.

Tubing might be connected to the inlet passageway through which asettable material can be injected. Alternatively a cartridge of thesettable material could be attached to or provide the inlet passageway,so that a plunger can be operated to inject the material within thecartridge into the cavity.

From a further aspect the invention extends to the insert of thisinvention as hereinbefore defined in combination with the settablematerial and means for injecting the material into the insert, thesettable material being of a nature that it will set when subjected toheat at the low refractory temperatures so as to be stable at thosetemperatures, but which will melt at the high refractory temperatures.

Suitable materials which might be used include clay together with abinder. The clay might be formed from a metal or non-metal oxide, suchas magnesia or aluminium or silicon containing materials.

The invention may be performed in various ways and preferred embodimentsthereof will now be described with reference to the accompanyingdrawings, in which:

FIG. 1 is a vertical section through a steel-making vessel incorporatinga plug defining a tap hole;

FIG. 2 is an enlarged cross-sectional view through the plug shown inFIG. 1 with a blocking insert of this invention therein; and

FIG. 3 is a perspective view of another embodiment of a blocking insertof this invention.

The steel-making vessel shown in FIG. 1 has an outer steel shell 1 linedinternally with a thick wall 2 of refractory bricks. An opening 3 at thetop provides for the insertion of steel-making materials. A plug 4 isfitted into the side wall of the vessel and defines a tap hole 5.

As can be seen from FIG. 1, and more particularly from FIG. 2, after anumber of uses the tap hole 5 becomes enlarged due to erosion and thusdoes not have a regular internal shape. A stage will be reached when theplug 4 needs to be replaced, but in the meantime various repairoperations may be carried out. This particular invention is concernedwith the need to block off the tap hole 5 during the stages of formationof the steel material within the vessel shown in FIG. 1. This isachieved by pushing an insert 6 into the tap hole 5. This insert hasouter and inner plates 7 and 8 formed from relatively thin steel sheetwhich will flex so as to adapt itself to the internal dimensions of thetape hole 5 as shown. Between the two plates 7 and 8 there is a tubularsupport member 9 defining a central passage-way 10 which has holes 11formed in its side walls which communicate with the open volume 12between the end plates 7 and 8. A supply hose 13 is connected to thetubular member 10.

In use, after the insert 6 has been pushed into place, a settablematerial comprising a clay and binder in wet form is injected throughthe supply hose 13 into the tubular member 10 and then, through theholes 11, into the open space 12 so that the whole volume between theend plates 7 and 8 is filled. At the temperatures experienced (for theheated steel-making vessel) the clay material will set rapidly so as toblock off the tap hole 5. Whilst a hose 13 has been illustrated forsupply of the settable material, it could advantageously be replaced, atleast at the furnace end by a rigid tube which can act also as the meansfor pushing the insert 6 home. For example the plate 8 could have alarge opening to receive the end of the rod, which will have a largecollar near the open end thereof to rest against the plate 8 during thepushing operation.

When the steel has been formed and the steel-making vessel is tipped toenable the molten steel to be poured off through the tap hole, the hotmolten material will rapidly melt the steel insert 6 and the set claymaterial, thus re-opening the tap hole 5. However, before this occurs,the slag level floating on top of the molten steel will have moved pastthe tap hole 5 so that little or no slag will be poured off through thetap hole 5, during the initial stages of pouring. Blocking off this taphole is also advantageous during the steel-making process as it preventsair entering the steel-making vessel through that passageway.

The former shown in FIG. 3 comprises a pair of end plates 14 and 15spaced apart by a pair of threaded bolts 16 which are secured to the endplates 14 and 15 by nuts 17 and 18. A backing plate 19 provides amounting for a support tube 20.

The end plates 14 and 15 are formed from cardboard material coated witha flame-retardant solution and cuts 21 are formed in the edges of thecardboard sheets to allow the edges to flex. In use the support tube 20is mounted onto a lance and the former is then introduced into theenlarged tap hole to be plugged. The end plates 14 and 15 adapt to theirregular shape of the tap hole and thus define between them an enclosedcavity into which a settable material is injected through the lance andthe support tube 20.

The support tube 20 could be constructed as a cartridge enclosing acharge of the settable material. A plunger could then be forced throughthe tube 20 to cause the settable material to be injected into thecavity between the two end plates 14 and 15. A similar operation couldbe achieved by replacing the supply hose 13 by a cartridge of settablematerial.

We claim:
 1. A tap hole blocking insert for a steel-making vessel,comprising a former including two spaced end plates defining betweenthem a cavity for a reception of a settable material between the endplates, one of the end plates having an inlet passageway therethroughfor the injection of a said settable material into said cavity, the endplates having outer peripheries that are exposed to the side walls ofthe tap hole into which the former is to be inserted, the end plateshaving sufficient flexibility to bend in contact with said side walls inorder to permit insertion of the former and having sufficient rigidityto retain the insert in the tap hole, the material of the end platesbeing fugitive at the temperature of molten steel so that the insertwill not block the flow of molten steel through the tap hole when thevessel is tilted sufficiently to bring the tap hole below the level ofthe molten steel in the vessel.
 2. A blocking insert as claimed in claim1, there being a hollow axial support member extending between the endplates, said inlet passageway communicating with the interior of saidaxial support member, said axial support member having holestherethrough, through which said settable material can pass.
 3. Ablocking insert as claimed in claim 1, and spacer rods which hold theend plates apart, said rods being screw threaded, and nuts on the screwthreaded spacer rods to adjust the distance between the end plates.
 4. Ablocking insert as claimed in claim 1, wherein said end plates haveradially extending cuts formed in the outer edges thereof.
 5. A blockinginsert as claimed in claim 1, the end plates being cardboard.
 6. Ablocking insert as claimed in claim 1, the end plates being sheet steel.7. A method of blocking a tap hole of a steel-making vessel, comprisingintroducing into the tap hole an insert comprising a former includingtwo spaced end plates defining between them a cavity for a reception ofa settable material between the end plates, one of the end plates havingan inlet passageway therethrough for the injection of a said settablematerial into said cavity, the end plates having outer peripheries thatare exposed to the side walls of the tap hole into which the former isto be inserted, the end plates having sufficient flexibility to bend incontact with said side walls in order to permit insertion of the formerand having sufficient rigidity to retain the insert in the tap hole, thematerial of the end plates being fugitive at the temperature of moltensteel so that the insert will not block the flow of molten steel throughthe tap hole when the vessel is tilted sufficiently to bring the taphole below the level of the molten steel in the vessel, the methodfurther comprising injection a settable material through said inletpassageway into said cavity and into contact with said side walls of thetap hole, said settable material being fugitive at the temperature ofmolten steel.